This invention relates generally to orthopedic appliances, more particularly to joint prostheses and especially to devices for the surgical repair of the human knee.
Of the multitude of skeletal joints found in the human body, the knee is generally regarded as being the most inherently unstable, due in part to the complex of interrelated types of motion to which the several knee elements are subjected during the normal acts of walking, running, climbing stairs and the like. These motions include relative sliding and rolling as well as rotation about both horizontal and vertical axes; and in the past, a considerable variety of mechanical approaches have been proposed in the attempt to approximate, through an artificial joint, the natural action of the human knee. Advanced conditions of disease or serious traumatic injury of the knee joint further complicate surgical repair and efforts to simulate the natural knee motion through use of a prosthesis.
Under circumstances wherein the condyles of the knee are beyond acceptable repair by means of surgical replacement of only the articular surfaces thereof, it has been common practice heretofore to attempt joint reconstruction by means of one or the other of two general types of prostheses, viz. a first type which relies on a mechanical hinge and the second which is characterized by a ball-and-socket arrangement. The former type has as typical objections the transmission of excessive torsional loads to the fixation interface between the prosthesis and the leg bones and the disposition of the transverse pivot axis in an unnatural location. The latter type of device is difficult to install in proper alignment during surgical implantation.
Accordingly, a general object of the present invention is to provide a new and improved joint prosthesis for the replacement of a seriously impaired human knee.
Another object of the invention is to provide a knee joint prosthesis which combines the mechanical strength of a pintle hinge with carefully limited rotational freedom.
Still another object of the invention is to provide a knee joint prosthesis of the type described which situates the horizontal pivot axis in a natural location posteriorly offset from the tibial-femoral intersect.
A further object of the invention is to provide a knee joint prosthesis of the type described which affords ease of alignment and assembly during its surgical installation.
A yet further object of the invention is to provide a knee joint prosthesis of the type described which incorporates a non-metallic shock absorber and bearing element that can be easily replaced.
These and other objects and features of the invention will become more apparent from a consideration of the following descriptions.